Chemical manufacture



Oct. 5, E954 c. D. KEITH CHEMICAL MANUFACTURE Filed May 19, 1951 ATTORNEYS Patented ct. 5, 1954 ETE@ 'EES PATENT OFFICE @HEMICAL MANUFACTURE Carl D. tlieith, Munster, Ind., assigner to Sinclair Refining Company, New York, N. Y., a. corporation of Maine 2 Claims.

My invention relates to the recovery of sulfur values in the form of elemental sulfur from hydrogen suliide-rich gases. More particularly, my invention relates to the recovery of sulfur from sour gases in a combined operation in which a mixture of colloidal sulfur and polythionic acids are produced in an aqueous reaction medium and the eluent is reacted separately in the liquid phase under elevated temperature to produce molten sulfur. My invention provides a simplified reaction system requiring very low capital investment which is particularly adapted to the recovery of sulfur values from the hydrogen sulde available in oil refinery gases.

According to my invention, the hydrogen sulfide gas stream, after removal in one of the usual ways from hydrocarbon gases, is rst oxidized in a partial combustion zone with oxygen or air in known manner to produce a mixture of hydrogen sulfide and sulfur dioxide in the approximate ratio of 2 to 1. The reaction temperature is about 1700 to 2000 F. The resulting gas stream is cooled by passage through a molten sulfur reactor in indirect heat exchange with the reaction mixture therein. The temperature is adjusted to about 100 to 150 F. and then the gas stream is reacted by dispersion in an aqueous medium at about 70 to 130 F. Under the reaction conditions, oxidation of the hydrogen sulde by the sulfur dioxide is effected and a dispersion of colloidal sulfur and polythionic acids in water is produced. The mixture is converted to molten sulfur by continuous withdrawal from the colloidal sulfur reactor and introduction to the molten sulfur reactor where the mixture is reacted in the liquid phase at about 250 to 350 F. Sufficient pressure is maintained to keep the aqeuous mixture in the liquid phase and molten sulfur is separated from the liquid reaction phase. Advantageously, unreacted gases are recovered from the molten sulfur reactor and recycled to the reaction by addition to the gas stream to the colloidal sulfur reactor.

My invention will be better understood by reference to the accompanying drawing which illustrates the ilow in simplied and diagrammatic form. The hydrogen sulfide-rich gas stream is divided by means of lines I and I I to charge a portion of the hydrogen sulde to combustion furnace I2 and a portion of the hydrogen sulde to colloidal sulfur reactor I3, respectively.

Air is introduced with the hydrogen sulfide charge to combustion furnace I2 through connection It in an amount suicient to oxidize the hydrogen sulfide to sulfur dioxide. The hot gas stream from combustion furnace I2 is passed by means of connection I5 to molten sulfur reactor I6. The hot gas stream is conducted through reactor I6 in indirect heat exchange with the reactants therein and passed by means of connection Il to a separate cooler It Where the gas stream is quenched by a spray of cooling Water through line I9. The effluent gas stream is passed through line 2&3 and cooler 2I Where the temperature is adjusted to less than about F. and then by line 22 to colloidal sulfur reactor I3; The sulfur dioxide charge is mixed with hydrogen sulde from line Il in the ratio of about 2 moles of hydrogen sulde to 1 mole of sulfur dioxide in manifolding system 23. The gas mixture is continuously bubbled into a body of aqueous medium which is maintained in a state of agitation in reactor I3 by means of stirrer 2d. The temperature of the aqueous reaction medium is controlled by recycling a portion of the liquor through connection 25, cooler '2e and line 2l'. Make-up water is added through line 28.

A portion of the aqueous reaction medium through reactor I3 is continuously withdrawn through line 29 and passed by means of pump 30 to molten sulfur reactor I6. Molten sulfur is produced in reactor I6, is withdrawn from the bottom of the reactor through line 3l and excess water is withdrawn through line 32. Unreacted gases from reactor I6 which predominate in sulfur dioxide are returned to the system by connection 33 to line I'I.

In operation, the hydrogen sulde combustion furnace operates at about 1700 to 2000 F. If desired, the hydrogen sulfide gas may be handled as a single stream by partial oxidation in furnace I2, in which case only enough air is added through connection I4 to oxidize about one-third of the hydrogen sulde to sulfur dioxide. The ratio of hydrogen sulfide to sulfur dioxide may be varied somewhat but I prefer to operate with at least one mole or an excess of sulfur dioxide to two moles of hydrogen sulfide. The molten sulfur reactor must be operated at a temperature above 248 F., the melting point of amorphous sulfur. I prefer an operating temperature of about 275 F. The reaction is maintained in the liquid phase by application of superatmospheric pressure. In the reactor, suspended elemental sulfur, largely in the colloidal state, is converted to molten sulfur and the polythionic acids are converted to molten sulfur, sulfur dioxide and sulfuric acid. The conversion of the polythionic acids to elemental sulfur is about 50 per cent. The sulfuric acid produced passes to drain with the excess water removed from reactor I6 while the sulfur dioxide may be recycled, if desired.

The reaction of the hydrogen sulde and sulfur dioxide mixture inrtlie colloidal sulfur reactor is maintained in the aqueous medium and at a temperature of about 70 to 130 F. Advantageously the temperature is at least 100 F. and within the range 100 to 115 F. The sulfur concentration in the aqueous reaction medium of reactor I3 should be built up to about 2per. cent before withdrawal to the molten sulfur reactor i6. The sulfur concentration may be Varied between about 2 and 50 percent. Conversions inthe colloidal sulfur reactor I3 exceed 90 per cent.

The process of my invention will be further illustrated by reference to the following examples:

S Example I Hydrogen sulde at 71.56 liters per hour, sulfur .dioxide at 41.2 liters per hour z and nitrogenat 213.1 liters per hour are `mixed andbubbled into a reaction Vmediumfcomprising' liters of .de-

ionized `water maintained in va liz-liter fluted flask equipped with a stirrer. The: temperature of thel reaction is maintained at 130 F. The feed gases are mixed and bubbled into `the reaction medium at a point where the stirrerbreaks up any large bubbles and insures thorough dispersionof the reactants. After a period'of 5 hours, thel analysis of the reaction. mixture is-as follows:

Per cent Total sulfur 5.88 Elemental sulfur 5.27 Polythionic acids (calculated as H2S4Os) 1.05 Sulfurdioxide 1 0.03

The reaction mixture` then is heated` to.275 F. under `pressure and the'aqueous suspension-of elemental sulfur and approximately50 per cent of the sulfur'available in thepolythionic 4acids -is converted to molten sulfur. 1Underthe Iconditions of the aboveexample, about 63 per cent conversion to brimstone is obtained, calculating per cent conversion from Athe followingv equation:

Percent Conversiongs. SLI-gspSl from polythionic acids*X 100 `gs.- total S infeed of SO2-PPMS Based upon 50% recoveryof sulfur from polythionic acids.

vExample II Following the ymethod*oftlixample I,-but at a reaction' temperature of 115 F., a reaction mixture after 5 hours having the following-analysis is obtained:

f'Per cent Total sulfur i7 .26 Elemental sulfur S6-.50 Polythionic acids (calculated as 5125400- 1.31 Sulfur dioxide 0.04

Reaction vof the' mixture at"'275 F. :to produce molten sulfur results in a-conversion; to brimstone ofabout 76 per cent.

4 Example III Following the method of Example I, but at a reaction temperature of 70 F., a reaction mixture after 5 hours having the following analysis is obtained:

Percent Total sulfur 7.53 Elemental sulfur 6.59 Polythionic acids (calculated as H2S4O 1.60 Sulfur dioxide 0.06

Reaction of themixture at 275 F. to produce molten sulfur results in a conversion to brimstone of about per cent.

Eample IV This example is conducted according to the 4method of Example I but starting in the initial stage at a temperature of less than F. and increasing the temperature to a maximum of F. by the heat of reaction. With a feed gas composition to the rst stage of 2 H28: 1.15 SO2: 6'N2, the feed rates of 71.56 liters per hour of hydrogen sulde, 41.2 liters per hour of sulfur 'dioxide and213.1 liters per hourof nitrogen, the

following reaetionmixture is obtained after a `5-hour run:

Per cent Total sulfur 7.05 Elemental sulfur 6.29 4Polythionic acids l(calculated as.H2S4Os) 1.27 Sulfur dioxide 0.07

Under the above conditions, the per cent conversion to brimstone after reaction of the mixture at 275 F. to produce molten sulfur is about 79 per cent.

Per cent Total sulfur 7.39 Elemental Asulfur 6.84 -Polythionicacids (calculated as HzSiOeL-- 0.94 Sulfur dioxide 0.04

Under the above conditions,- the per cent conversion to brimstone after reaction of the mixture at 275 F. to producemclten sulfur is about 84 per cent.

Example VI Thisvexampleis conducted according to the method of fExample.A I but starting. in the initial stage at' a temperature of. less than 100 F..and increasing the temperature .to a maximum of 110 by the heat of reaction. With a feed gas composition lto the rst stage of 2.3 H25: 1602: '6 N2, the .feed rates of.82.4 liters per hour of hydrogen subida-35.7 8 liters per hour of4 sulfur dioxide and.2l3.1 liters per vhourof nitrogen, the following reaction vmixture is obtainedafter Ia 5-hour run:

. Per cent Total sulfur 7.75 Elemental sulfur `7.51 Polythionic acids (calculatedas H2S4Os) y0.42 Sulfurdioxide 0.01

Under the above conditions, the per cent conversion to brimstone after reaction of the mixture at 275 F. to produce molten sulfur is about 78 per cent.

I claim:

l. In the recovery of elemental sulfur from a hydrogen sulfide-rich gas stream, the method which comprises partially oxidizing hydrogen sulfide with air to produce a mixture of hydrogen sulde and sulfur dioxide in the gas stream in the approximate ratio of 2 to 1, cooling the gas stream by passing it through a molten sulfur reactor in indirect heat transfer with the reactants therein, adjusting the temperature of the gas stream to about 100 to 150 F., reacting the mixture of hydrogen sulfide and sulfur dioxide in aqueous medium at a temperature of about 70 to 130 F. in a second reaction vessel, Withdrawing the aqueous reaction mixture from the second reaction Vessel and reacting it in the References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,546,048 Vogel July 14, 1925 1,832,448 Coleman et al Nov. 17, 1931 1,901,249 Lincoln Mar. 14, 1933 1,904,424 Edmonds et al Apr. 18, 1933 1,925,198 Melvill Sept. 5, 1933 2,389,810 Odell et al NOV. 27, 1945 2,563,437 'Townend et al Aug. 7, 1951 

1. IN THE RECOVERY OF ELEMENTAL SULFUR FROM A HYDROGEN SULFIDE-RICH GAS STREAM, THE METHOD WHICH COMPRISES PARTIALLY OXIDIZING HYDROGEN SULFIDE WITH AIR TO PRODUCE A MIXTURE OF HYDROGEN SULFIDE AND SULFUR DIOXIDE IN THE GAS STREAM IN THE APPROXIMATE RATIO OF 2 TO 1, COOLING THE GAS STREAM BY PASSING IT THROUGH A MOLTEN SULFUR REACTOR IN INDIRECT HEAT TRANSFER WITH THE REACTANTS THEREIN, ADJUSTING THE TEMPERATURE OF THE GAS STREAM TO ABOUT 100* TO 150* F., REACTING THE MIXTURE OF HYDROGEN SULFIDE AND SULFUR DIOXIDE IN AQUEOUS MEDIUM AT A TEMPERATURE OF ABOUT 70* TO 130* F. IN A SECOND REACTION VESSEL, WITHDRAWING THE AQUEOUS REACTION MIXTURE FROM THE SECOND REACTION VESSEL AND REACTING IT IN THE MOLTEN SULFUR REACTOR IN THE LIQUID PHASE AT A TEMPERATURE OF ABOUT 250* TO 350* F. AND RECOVERING MOLTEN SULFUR FROM THE LIQUID REACTION PHASE. 